Recently a Stirling engine having excellent theoretical thermal efficiency receives attention to recover exhaust heat of an internal combustion engine mounted on a vehicle such as a passenger car, a bus, and a track or plant exhaust heat. There is known a technique disclosed in Patent Document 1 as a piston apparatus applicable to an external combustion engine including the Stirling engine.
A piston of a heat engine disclosed in Patent Document 1 is one which is applied to a type of Stirling engine in which a displacer is used. The displacer is driven by action of a working medium which repeats compression and expansion in a working space in association with reciprocating motion of the piston in a cylinder. The piston of the heat engine includes a compressing chamber, a check valve, and an orifice. The compressing chamber is formed inside the piston, and temporarily accumulates the working medium compressed in the working space. The check valve prevents the working medium in the compressing chamber from flowing back into the working space. The orifice ejects the working medium in the compressing chamber to a clearance portion between the piston and the cylinder.
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2000-46431